Overclocking a Starfox game cartridge

Some of our younger readers will never have experienced this before, but back in the day your video games would slow way down if there were too many moving objects on the screen. The original Castlevania comes to mind, but many will remember the problem while playing the fantastically three-dimensional Super Nintendo game Starfox. [Drakon] isn’t putting up with that hardware shortfall any longer, he hacked this cartridge to run at 42 MHz, twice as fast as the design spec.

We only occasionally look in on the cart hacking scene so it was news to us that three different versions of a pin compatible chip were used in this hardware. The first two suffer from the slowdown problem, but the final revision (SuperFX GSU 2) doesn’t. It can also be overclocked as high as 48 MHz but because of the video frame rate you won’t see added improvement with the extra 6 MHz.

[Drakon] used a Doom cartridge as a guinea pig because it offers the most RAM, and set to work rerouting the traces for the ROM chip to an EEPROM so that the hardware can be used with different games. He also took this opportunity to patch in the faster clock signal.

21 thoughts on “Overclocking a Starfox game cartridge”

The fact that the video game console offloaded processing to the cartridge warrants a “hack” qualification itself! It was done to add extra features features (e.g. more memory, processing power) and extended the useful service life of the console, at the expense of higher-priced cartridges.

BTW, games still slow down if there are too many moving objects onscreen.

The framerate might drop but the frame-to-frame interval is factored into acceleration/movement/etc. calculations to keep the game itself running at the same speed regardless of the framerate. Most games back then used fixed speeds for everything regardless of how often the frame finished and relied on the framerate limiter not to go insane when little was going on. There was little point in wasting development time and processor cycles on doing the extra multiplications/powers. Not that modern devs always get this right – it’s an easy mistake to make sometimes and a hard one to spot.

Frame-skipping was far beyond the capabilities of an SNES. If a game wasn’t done with the next frame by the time the VBlank period ended and stuff started drawing, everything got delayed for another frame.
The fixed speed used was … the clock speed of the console. Why would you waste precious ROM space making a game with a VERY specific hardware target be multi-platform aware? If you finish early, just idle until your VSync interrupt hits.

Caveat: if you cared about PAL SNESes having more clock cycles per frame and fewer frames per second, you coded your game to make it easy to change the timings. No one did. Almost without exception, they ran slow in Europe since they were locked to VSync.

@Jaybee (can’t reply)
I’m not sure where you’re going with this besides repeating what I just said? He ended saying that even games today slow down. I pointed out they don’t thanks to framerate independence.

Another trick besides soldering is to use a ‘donor cart’ and something like a Game Genie’s passthrough connector. You just plug the Doom cartridge into a connector like the one inside the SNES. It has the ‘extra’ pins go directly to the card edge (plug) of your custom board while the other pins go to sockets on the board. Then put Flash ROM on your board, program it, and you’re good to go!

The nice thing about this is that you don’t risk breaking your (getting rarer!) precious Doom cartridge.